The present invention relates to systems and methods for removing material, such as obstructions and partial obstructions, from any body lumen of a mammalian subject, such as a blood vessel, a portion of the gastrointestinal tract, a portion of the dural spaces associated with the spinal cord, or the like. More particularly, the present invention relates to systems, system components, and methods for removing material from a lumen of a mammalian subject using an advanceable, rotating cutter assembly.
Removal of atherosclerotic obstructions and partial obstructions using rotating cutter assemblies is a well-established therapeutic intervention. Numerous atherectomy methods and devices have been conceived and developed. Most of these systems involve placement of a guide wire, a guiding catheter and a cutting device in proximity to an obstruction or partial obstruction in a blood vessel and then advancing and rotating the cutting device to cut or ablate the obstruction.
The following U.S. patents describe many types and specific features of atherectomy devices: U.S. Pat. Nos. 4,898,575; 5,127,902; 5,409,454; 5,976,165; 5,938,670; 5,843,103; 5,792,157; 5,667,490; 5,419,774; 5,417,713; 4,646,736; 4,990,134; 4,445,509; 5,681,336; 5,695,507; 5,827,229; 5,938,645; 5,957,941; 5,019,088; 4,887,613; 4,895,166; 5,314,407; 5,584,843; 4,966,604; 5,026,384; 5,019,089; 5,062,648; 5,101,682; 5,112,345; 5,192,291; 5,224,945; 4,732,154; 4,819,634; 4,883,458; 4,886,490; 4,894,051; 4,979,939; 5,002,553; 5,007,896; 5,024,651; 5,041,082; 5,135,531; 5,192,268; 5,306,244; 5,443,443; 5,334,211; 5,217,474; 6,183,487; 5,766,190, 5,957,941 and 6,146,395. These U.S. patents are incorporated by reference herein in their entireties.
Despite the many and varied approaches to atherectomy systems and methods exemplified by the U.S. patents cited above, many challenges remain in providing systems and methods for removing material from a lumen, such as a blood vessel, safely and reliably and without causing complications. The safety and reliability of the system is manifestly critical. Recovery of the debris generated during an atherectomy operation, or maceration of the debris to a particle size that will not produce additional blood vessel clogging or damage, is essential. The flexibility and size of the system is also an important feature. Control features and the ease of use of the system by a surgeon or other medical professional are additional important features.
One of the particular challenges of removing material from the interior of lumens is that the drive and cutter assemblies must be small enough and flexible enough to travel, over a guidewire, to a desired material removal site, such as the site of an obstruction or occlusion. Yet, the drive and cutter assemblies must be large enough and have structural integrity sufficient to operate reliably and effectively to cut or ablate the obstruction. Additionally, removal of the debris from the material removal site using an aspiration system is generally desirable. The drive and cutter assemblies therefore desirably incorporate a debris removal system as well.
The size and consistency of the material comprising the obstruction are frequently not well characterized prior to introduction of the material removal device. Thus, although devices and cutters having different sizes and properties may be provided, and may even be interchangeable on a materials removal system, it is difficult to ascertain which combination of features is desired in any particular operation prior to insertion of the device. The use of multiple cutter assemblies having different properties during a materials removal operation is inconvenient at best, since it requires removal of each independent device and interchange of the cutter assemblies, followed by reinsertion of the new cutter assembly, or of a new device entirely. Interchange and reinsertion of cutter assemblies is time consuming and generally deleterious to the health and condition of the patient undergoing the procedure.
Many different types of expandable cutters have been conceived in an effort to provide a cutter having a small diameter profile that may be delivered to and removed from the site of the desired material removal, and that is expandable at the site to provide a larger diameter cutter. The following U.S. patents disclose various approaches to expandable cutter assemblies: U.S. Pat. Nos. 5,540,707; 5,192,291; 5,224,945; 5,766,192; 5,158,564; 4,895,560; 5,308,354; 5,030,201; 5,217,474; 5,100,425; and 4,966,604. These patents are incorporated by reference herein in their entireties.
Although many approaches to expandable cutter assemblies have been developed, none of these approaches has, to date, been known to be implemented in a commercially successful atherectomy system.
One aspect of the present invention involves the therapeutic application of methods and systems for translumenal microsurgery using advanceable, rotating cutter assemblies to conditions and disorders in addition to atherectomy and cardiology applications. Methods and systems for translumenal microsurgery using advanceable, rotating cutter assemblies of the present invention may be implemented, for example, in treatment of blood vessel conditions and for removal of accumulations of materials in blood vessels in applications other than cardiology and in blood vessels remote from the heart; in treatment of benign prostate hyperplasia; in the treatment of gynecological conditions involving accumulation of material in fallopian tubes and elsewhere, such as fibrotic disease; in treatment of urological conditions, such as kidney stones; in treatment of gallbladder conditions, such as gall stones; and in the treatment of spinal cord and dural tube conditions, such as stenoses of the spinal canal.
Methods and systems of the present invention involve placement of a material removal component, referred to herein as a xe2x80x9ccutterxe2x80x9d or xe2x80x9ccutter assemblyxe2x80x9d within a lumen of a mammalian subject using conventional techniques, such as guidewires and guiding catheters. The intralumenal material removal system includes a cutter assembly positionable in the lumen of a mammalian subject and operably connected to system controls, mechanical and power systems by means of a rotating drive shaft and generally, a stationary guide catheter. The cutter assembly preferably comprises a distal cutting or abrading head having one or more cutting and/or abrading surfaces that is advanceable by translating the drive shaft and rotatable by rotating the drive shaft. The cutter assembly may comprise two or more cutters having different properties.
According to a preferred embodiment of the present invention, the cutter assembly comprises a cutter that is adjustable between a smaller diameter condition, in which it may be guided to and withdrawn from the desired material removal site, and a larger diameter condition, in which it may be operated during a material removal operation. The cutter may thus be introduced to and withdrawn from the material removal site in a retracted, smaller diameter condition that facilitates translation and navigation of the device through various lumens, such as blood vessels. The expandable cutter may be selectively expanded at the material removal site to facilitate cutting, removal and aspiration of the material desired to be removed.
The material removal system preferably provides removal of debris, generally via aspiration through one or more material removal ports in the cutter assembly or another component in proximity to the cutter assembly. Debris generated during a material removal operation is removed by aspiration through the material removal ports and withdrawn through a sealed lumen formed, for example, between the cutter assembly drive shaft and a catheter. The sealed lumen is connectable to a vacuum source and aspirate collection system.
According to another preferred embodiment, the materials removal device of the present invention comprises dual cutting and/or abrading members, one of which is expandable and one of which has a fixed diameter. In one embodiment, a fixed diameter cutter is mounted distal to an expandable diameter cutter. The fixed diameter cutter may take any of a variety of configurations and, according to one embodiment, has a generally ovoid configuration and a plurality of cutting flutes. The fixed diameter cutter may also be provided with ports and/or cutouts that may be selectively employed as aspiration or infusion ports. The expandable diameter cutter, positioned proximal to the fixed diameter cutter, may also be provided with ports that may be selectively employed as aspiration or infusion ports.
In one embodiment, the cutter assembly drive shaft operates bidirectionally and the adjustable diameter cutter is expanded or retracted selectively and controllably upon rotation in opposite directions. Upon rotation of the drive shaft and dual cutter assembly in a first direction, the fixed diameter cutter is used as the primary cutting head and the expandable cutter remains in a smaller diameter condition, while upon rotation of the dual cutter assembly in a second direction, opposite the first, the expandable cutter is in a larger diameter condition and serves as the primary cutter. The present invention uses hydrodynamic, centrifugal and/or frictional forces to expand and contract the dual cutter assembly, thereby obviating the need for additional actuation systems, which add considerable complexity and rigidity to such systems.
Liquid infusion may be provided in proximity to the cutter assembly in addition to or alternatively to aspiration. Infusion of liquids may be used to provide additional liquids for materials removal or to deliver lubricating fluids, treatment agents, contrast agents, and the like. Infusion of fluids in proximity to the area of a material removal operation may be desirable because it tends to reduce the viscosity of the materials being removed, thus facilitating removal through relatively small diameter lumens. Infusion of liquids also desirably tends to reduce the volume of blood removed during the operation. According to one embodiment, a sealed lumen formed between the cutter assembly drive shaft and a catheter may alternatively and selectively be used as an aspirate removal system and an infusion system. The sealed lumen may thus be selectively connectable to a vacuum source and aspirate collection system for aspiration, and an infusion source for infusion of liquids. Ports in or in proximity to the cutter assembly may be thus be employed, selectively, as aspiration and infusion ports.
According to another embodiment, an infusion system may be provided in addition to and independent of the aspiration system. In one embodiment, an infusion sleeve is provided that extends distal to the material removal element. The infusion sleeve is sealed for the length of the catheter and incorporates distal infusion ports. The infusion sleeve preferably extends through the lumen formed by the drive shaft and may be fixed, or preferably, translatable with respect to the dual cutter assembly.
Yet another aspect of the present invention involves the implementation of certain automated and selectable control features. Thus, according to one embodiment, a material removal system of the present invention implements control features based on an operator""s input of specified parameters. Specified parameters may include, for example: lesion length, lesion type and character, such as calcified, fibrotic, lipid/fatty, and the like; and/or historical factors, such as restenosis; rate of blood flow; volume of blood flow; percentage of restriction; lumen type and/or location; lumen diameter; desired rotation rate and/or rotation profile for the cutter assembly; desired advance rate and/or advance profile for the cutter assembly; desired aspiration rate and/or profile; desired infusion rate and/or profile; and the like. Based on the specified parameters input by the operator, an automated cutter assembly control unit may calculate and implement automated operating conditions, such as: cutter assembly rotation rate and profile; cutter assembly advance rate and profile; aspiration rate and profile; infusion rate and profile; cutter assembly size and type; and the like.
Another aspect of systems and methods of the present invention involves temperature sensing and control during a material removal operation. Localized temperature increases to temperatures above ambient body temperature can produce an inflammatory response at localized sites, such as at the site of a material removal operation. Localized inflammatory responses can cause a lumen, such as an artery, to narrow or to close completely. Additionally, certain types of plaques and lesions (xe2x80x9cvulnerable plaquesxe2x80x9d) are more prone and more sensitive to increased temperatures during a material removal operation using an advanceable and rotatable cutter assembly. Temperature increases during a material removal operation at such vulnerable plaques may produce emboli and may contribute to heart attacks. Restonosis may also occur in a blood vessel following a material removal operation as a consequence of elevated temperatures during the material removal operation.
According to another embodiment of material removal systems and methods of the present invention, a temperature sensor is mounted in proximity to the site of material removal, preferably at the site where the cutter assembly engages the material to be removed, such as a lesion. The temperature sensor is preferably operably connected with a control unit and/or a display device to provide temperature monitoring during a material removal operation. Temperature monitoring at the site of material removal may be integrated with control features in an active or passive manner. In a passive control embodiment, a temperature monitoring feature is provided, enabling the operator performing a material removal procedure to monitor the temperature at the material removal site and manipulate (e.g., adjust advancement and/or rotation of) the cutter assembly appropriately to minimize increases in temperature at the site of material removal. In an active control embodiment, data relating to the temperature, or temperature increases, at the material removal site is provided, intermittently or continuously, to a control system. The control system analyzes the temperature data and minimizes changes in temperature at the site of material removal by automatically changing the advancement and/or rotation profile of the cutter assembly based on the temperature profile. Additional features may be integrated in the control system including, for example, aspiration and infusion flow and flow rates, which may be used to reduce the temperature at the material removal site.